This invention relates to a floating type head slider on which there is mounted a transducer such as a magnetic head, etc. for carrying out recording and/or reproduction of information signals with respect to a disc-shaped recording medium on which information signals are recorded, such as a magnetic disc or magneto-optical disc, etc., a floating type head device using such a head slider, and a disc drive using such a head device.
Hitherto, as the internal memory unit of an information processing device such as a computer, etc., or the external memory unit for a computer, disc drive mechanisms (hereinafter simply referred to as disc drive depending upon circumstances) using, as a recording medium, a hard disc which is the magnetic disc having rigidity, are used.
Such a disc drive comprises, as shown in FIG. 1, a magnetic disc 1 rotationally operated in the direction indicated by arrow R.sub.1 in FIG. 1, at a constant angular velocity by the spindle motor, and a magnetic head unit 2 for scanning the signal area of the magnetic disc 1 extending over the inner and outer circumferences thereof. This magnetic head unit 2 is of a structure as shown in FIG. 2 in which a magnetic head 4 is integrally attached to a head slider 3 moving on the signal recording area of the magnetic disc 1. The magnetic head unit 2 is supported at the front end side of a rotational arm 5 rotationally operated in the direction indicated by arrow X.sub.1 in FIG. 1, with the support shaft being as the center by the voice coil motor. Namely, the magnetic head unit 2 is adapted so that when the voice coil motor is driven so that the rotational arm 5 is rotationally operated, the unit 2 is caused to undergo movement operation in the direction indicated by arrow X.sub.1 in FIG. 1 extending over inner and outer circumferences of the magnetic disc 1 rotationally operated, thus to carry out recording/reproduction of predetermined information signals with respect to recording tracks of the magnetic disc 1.
In this example, the head slider 3 is supported at the front end of the rotational arm 5 through a displaceable elastic (resilient) supporting member in the directions to come into contact with the surface of the magnetic disc 1 and to become away therefrom.
Meanwhile, the head slider 3 on which the magnetic head 4 is provided is adapted as shown in FIG. 2 so that a pair of side rails 6a, 6b forming air bearing are formed between the head slider 3 and the surface of the magnetic disc 1 on the both sides of the lower surface side opposite to the magnetic disc 1 to allow the portion between these side rails 6a, 6b to be a recessed portion 7. These side rails 6a, 6b are formed in a manner substantially in parallel to the tangential direction of recording tracks formed on the magnetic disc 1 when the magnetic head unit 2 is opposed to the magnetic disc 1. At the air inflow end side opposite to the rotational direction of the magnetic disc 1 of the side rails 6a, 6b, taper portions 8a, 8b are formed.
In this example, the magnetic head 4 is provided at the end portion of the air outflow side opposite to the air inflow side of the head slider 3.
The head slider 3 formed in a manner as described above is adapted when it is caused to be close to the surface of the magnetic disc 1 rotationally operated as shown in FIG. 1, it is caused to undergo floating force produced by air flow flowing into the portion between the side rails 6a, 6b and the surface of the magnetic disc 1 in accordance with rotation of the magnetic disc 1 so that it is floated from the surface of the magnetic disc 1. When the head slider 3 is floated from (i.e., above) the surface of the magnetic disc 1, the magnetic head 4 attached on the head slider 3 is also floated from the surface of the magnetic disc 1 as shown in FIG. 3, and is moved on the magnetic disc 1 in the state where a floating quantity d of a very small spacing (distance) is maintained between the magnetic head 4 and the surface of the magnetic disc 1. As stated above, as the result of the fact that the head slider 3 and the magnetic head 4 are moved on the magnetic disc 1 in a state floated from the surface of the magnetic disc 1, abrasion and/or damage of the magnetic disc 1 and the magnetic head 4 can be prevented.
In this example, the floating quantity from the magnetic disc 1 of the magnetic head 4 of the disc drive using the floating type head is approximately 0.1 .mu.m.
When the head slider 3 of the floating type constructed in this way is used, even in the case where uneven portions exist to some degree on the surface of the magnetic disc 1, differences between these uneven portions is absorbed, thus permitting floating quantity d from the magnetic disc 1 of the head slider 3 and the magnetic head 4 to be substantially constant.
However, in the above-described head slider 3 of the floating type, in the case where any impact is applied to the magnetic disc 1, or in such cases that uneven portion or undulated portion of the surface of the magnetic disc 1 is great, there is the possibility that floating quantity d from the surface of the magnetic disc 1 may vary to much degree.
Moreover, in the case where the magnetic disc 1 is rotated with the angular velocity being constant, linear velocity would be varied at the inner and outer circumferences. Namely, the linear velocity of the magnetic disc 1 gradually becomes higher according as the movement position shifts from the inner circumferential side toward the outer circumferential side. For this reason, the floating quantity d from the magnetic disc 1 of the head slider 3 at the outer circumferential side and that at the inner circumferential side of the magnetic disc 1 would differ to much degree. Namely, the floating quantity d from the magnetic disc 1 of the head slider 3 varies in dependency upon the linear velocity. As a result, fluctuation (change) of the floating quantity corresponding to the linear velocity takes place.
On the contrary, when the rotational arm 5 is rotated in the direction indicated by the arrow X.sub.1 in FIG. 4 on the surface of the magnetic disc 1, with a support shaft 8 being at the center, the head slider 3 attached to the front end of the rotational arm 5 is moved so as to trace a circular arc-shaped locus without experiencing linear movement in the radial direction of the magnetic disc 1. For this reason, as shown in FIG. 5, the center line P.sub.1 of the head slider 3 is shifted from the tangential direction S.sub.1 of the recording track T.sub.1 of the magnetic disc 1, so skew angle .theta.s would take place. This skew angle .theta.s changes depending upon the position from the center of the magnetic disc 1. Namely, when the skew angle .theta.s becomes large, efficiency of change with respect to the floating force of the dynamic pressure between the surface of the magnetic disc 1 and the head slider 3 is lowered. As a result, the floating quantity d becomes small.
From facts as described above, the floating quantity of the head slider 3 which becomes large at the outer circumferential side of the magnetic disc 1 where the linear velocity becomes large would be lowered as the result of the fact that the skew angle .theta.s becomes large resulting from the fact that the head slider 3 is moved toward the outer circumferential side of the magnetic disc 1. In this case, fluctuation (change) of the floating quantity d of the head slider 3 based on change of linear velocity at inner and outer circumferences of the magnetic disc 1 becomes change following change of the linear velocity. However, fluctuation (change) of the floating quantity d by change of the skew angle .theta.s becomes the secondary non-linear fluctuation in which it becomes large at the inner and outer circumferences of the magnetic disc 1 and becomes small at the central portion in the radial direction of the magnetic disc 1. Accordingly, as long as the head slider 3 constituted as shown in FIG. 2 is employed, it would become difficult to take balance between the linear velocity and the skew angle .theta.s extending over the entire range in the radial direction of the magnetic disc 1.
For this reason, by the interaction between fluctuation (change) of the floating quantity d of the header slider 3 based on change in the linear velocity extending over the inner and outer circumferences of the magnetic disc 1 rotating at a constant angular velocity and fluctuation (change) of the floating quantity based on change of skew angle .theta.s by movement of the head slider 3, the spacing (distance) between the magnetic head 4 and the magnetic disc 1 would be unable to be maintained constant. As a result, it becomes impossible to precisely control intensity of the magnetic field applied from the magnetic head 4 to the magnetic disc 1, giving rise to deterioration of the recording/reproduction characteristic of information signals. Thus, there is the possibility that precise recording and/reproduction of information signals may be unable to be carried out.
As the floating type head slider of this kind, there is a head slider described in the Japanese Patent Publication No. 56635/1988, incorporated herein by reference.